1. Field of the Invention
The present invention relates to an image processing system capable of appropriately cope with unstable power supply.
2. Description of the Background Art
As one type of image processing apparatuses as electronic equipment, an image forming apparatus (typically a copy machine) for forming an image on a sheet of recording paper has been introduced to many places of business (companies and offices). In such a place of business, it is a common practice to have an image forming apparatus having a printer function or copy function connected to a network and to share the apparatus by a plurality of users. An MFP (MultiFunction Peripheral) as one type of such image forming apparatuses has a plurality of basic operational modes including a copy mode, a facsimile mode (hereinafter facsimile will be also denoted as FAX), a network compatible printer mode and a scanner mode.
Recently, in places of business, increase in power consumption resulting from use of personal computers (also referred to as PCs) allocated to each person and installation of a large number of electronic apparatuses including a plurality of MFPs has come to be a cause of concern. To meet the demand of energy saving, power consumption of each apparatus as a single body has been reduced, for example, by improving specifications of each electronic apparatus, including the MFP.
A conventional image processing apparatus is basically designed on the premise of stable power supply. By way of example, a function of distributing one print job to a plurality of MFPs (hereinafter also referred to as “cluster printing”) to increase apparent speed of output, a power saving function and so on are all proposed taking it for granted that power supply is always stable. Different from a note type PC or a portable terminal provided with a battery, for an image processing apparatus, it has been unnecessary to consider any special measure to cope with low battery, or to prepare for expected power outage time, and practically such measures have not been taken.
Considering electricity supply situations of late, however, the stable power supply that has been long taken for granted (guaranteed) may no longer be realistic. Possibility of reduction in power supply or interruption of power supply (outage) is no longer negligible. Public restriction of power use (for example, planned outage) has actually been enforced. Conventional energy-saving measures taken in each apparatus is insufficient to cope with such a situation. Therefore, it has been desired to implement appropriate measures in each image processing apparatus as well as to appropriately manage and control a plurality of image processing apparatuses with limited power supply, in order to prevent problems such as abrupt outage caused by power shortage.
By way of example, Japanese Patent Laying-Open No. 11-17875 (hereinafter referred to as '875 Reference) discloses a technique of shifting timing of power-on, in order to prevent a plurality of copy machines of one floor from simultaneously entering warm-up mode. This approach reduces influences on the power supply voltage and, though for a short period of time, power consumption can be reduced.
In connection with the cluster printing using a plurality of image processing apparatuses simultaneously, Japanese Patent Laying-Open No. 2003-177895 (hereinafter referred to as '895 Reference) discloses a technique of solving a problem of image missing experienced when one print job is divided and output by a plurality of image forming apparatuses, if speed of data transfer from a print server to image forming apparatuses is slower than the printing speed of the image forming apparatuses. According to this technique, the print job is divided anew to reduce the number of image forming apparatuses to be used.
As described above, it is necessary to implement appropriate measures in each image processing apparatus to prevent problems such as abrupt outage caused by power shortage. Further, it is necessary to appropriately manage and control a plurality of image processing apparatuses. If cluster printing is to be done with priority given on the speed of output, a plurality of image processing apparatuses are used simultaneously and, therefore, power consumption increases whereas the processing time becomes shorter. This is also true whenever one job is executed using a plurality of image processing apparatuses, not only in the case of cluster printing. Therefore, measures to cope with reduced power supply are particularly necessary when one job is executed using a plurality of image processing apparatuses.
The cluster printing, in which one job is executed by a plurality of image forming apparatuses simultaneously, however, is not considered in '875 Reference. Further, '895 Reference has no consideration of abrupt outage caused by unstable state of power demand/supply or a situation in which sufficient power supply to a plurality of image forming apparatuses is difficult.
In view of the problems described above, it is desirable to provide an image processing system capable of appropriately cope with a situation of unstable power supply such as reduction of power supply, and capable of appropriately processing a job that uses a plurality of image processing apparatus such as a cluster printing job.